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Environ. Sci. Technol. 2000, 34, 4103-4110

Correlating Selective Supercritical Fluid Extraction with Bioremediation Behavior of PAHs in a Field Treatment PlotSTEVEN B. HAWTHORNE* AND CAROL B. GRABANSKI Energy and Environmental Research Center, University of North Dakota, P.O. Box 9018, Grand Forks, North Dakota 58202Selective supercritical fluid extraction (SFE) behavior of PAHs from manufactured gas plant (MGP) site soils was determined on untreated soil and on soils collected after1/2 year and 1 year of bioremediation in a field land treatment plot. Sequentially stronger SFE conditions gave selective extraction of PAHs associated with “fast” (or“rapidly desorbing”), “moderate,” “slow,” and “very slow” sites on the soil collected before and during bioremediation. While all PAHs from the untreated soil showed“stair-step” extraction curves (with molecules in each of the four “fast” to “very slow” SFE fractions), two- and three-ring PAHs were found mostly in the “fast” fraction,while the five- and six-ring PAHs were found almost completely in the “slower” fractions. SFE comparisons of the untreated and bioremediated soils showed thatbioremediation only removed PAH molecules which were found in the “fast” fractions by SFE and that remediation for 1 year did not result in the migration of PAHs from “slower”to “faster” sites. One hour SFE of the untreated sample at the mildest condition (120 bar, 50 °C) gave good quantitative agreement with removals achieved after 1 yearof bioremediation, and SFE correctly predicted that two- and three-ring PAHs would show ∼90% removals, four-ring PAHs ∼50% removals, and five- and six-ring PAHs
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